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Author Topic: Low Voltage DC - DC multiplier  (Read 3157 times)

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Offline jsmokerTopic starter

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Low Voltage DC - DC multiplier
« on: February 16, 2011, 08:43:08 AM »
Hey all,

I'm trying to power a common LED (~2V) with a 0.3V source and I've been trying to figure out how to bump up the voltage.  For the record, the 0.3V source has some good amperage behind it for use with a charge pump (CP), but i can't seem to find one to fit the bill. I have a MAX660 voltage doubler on hand but it require minimum 2.5V.  I've looked up 555 timer chips to create an oscillation to use with multiplier circuits but even the 555 needs 0.7V.  The lowest voltage CP chip I could find still required 0.5V.

Thanks!

Offline newInRobotics

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Re: Low Voltage DC - DC multiplier
« Reply #1 on: February 16, 2011, 11:22:32 AM »
"Computer games don't affect kids; I mean if Pac-Man affected us as kids, we'd all be running around in darkened rooms, munching magic pills and listening to repetitive electronic music." - Kristian W

Offline TrickyNekro

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Re: Low Voltage DC - DC multiplier
« Reply #2 on: February 16, 2011, 12:36:15 PM »
Just out of curiosity what are you using? I never saw a 0.3V supply so far, and I really can't imagine what it may be...
For whom the interrupts toll...

Offline Afroman

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Re: Low Voltage DC - DC multiplier
« Reply #3 on: February 17, 2011, 12:36:38 AM »
Linear Technology has been doing a large push the last couple of years into the energy harvesting field. Check out linear.com and they will have lots of solutions.

Offline Soeren

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Re: Low Voltage DC - DC multiplier
« Reply #4 on: February 17, 2011, 07:24:35 PM »
Hi,

I'm trying to power a common LED (~2V) with a 0.3V source and I've been trying to figure out how to bump up the voltage.  For the record, the 0.3V source has some good amperage behind it for use with a charge pump (CP),
Solar cell?

If you describe the project a bit more, it would be easier to help you.
What is the supply?
Why is it only 0.3V?
Is the 0.3V a stable regulated voltage?
Don't you have any other voltages in-circuit?
Is the 0.3V a part of an output or such?

A schematic might reveal other options/voltages/places to tap.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline jsmokerTopic starter

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Re: Low Voltage DC - DC multiplier
« Reply #5 on: February 17, 2011, 08:49:49 PM »
It's a Seebeck effect thermoelectric junction (a glorified thermocouple).  I want to show it's effect with a LED for demonstration purposes.  When you heat up one side it creates current potential.  I've gotten it up to ~0.5-0.6V but with very high heat and only for a very short time period...I don't want to burn the coating surrounding it.  Voltage is a function of heat so it's not regulated.  I'm using a single multimeter so I can't give an exact correspondance but at 0.3V I'm getting around .2A.  I was roughly estimating on possibly getting a x7 boost in voltage which might correspond to a 1/14th drop in amperage assuming 50% efficiency which would still give me ~.01A which is still good enough for an LED.

Offline Soeren

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Re: Low Voltage DC - DC multiplier
« Reply #6 on: February 17, 2011, 09:15:28 PM »
Hi,

Ahh, I see.
The easy way out would be to series connect some (perhaps smaller size) elements for a higher voltage.

0.3V might just be used with germanium transistors to create a boost circuit, but germanium transistors can be hard to find, expensive and they're leaky and slow compared to silicium.

Or... Cheat a little bit and make a circuit driven from 2 cells (3V) using eg. an op-amp with the gain set suit the voltage range possible - If you use PWM, this circuit could even give a pretty linear function between input voltage and percieved brightness of the LED.
After all, if it's just to demo the function, it should not matter that the monitor is battery powered.

Or... Use an oldfashioned analog meter to show the effect.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline Admin

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Re: Low Voltage DC - DC multiplier
« Reply #7 on: February 17, 2011, 09:35:09 PM »
Quote
It's a Seebeck effect thermoelectric junction (a glorified thermocouple).  I want to show it's effect with a LED for demonstration purposes.
A coworker and I had a ocean bacteria battery (don't ask) that outputs about 0.3V and ~10mA.

We were required to demonstrate it powering something.

We used a charge pump to get the voltage up, and the output from that went to a solar engine.

What a solar engine does is store energy until it reaches the threshold you want, then releases it all at once. It's very popular among the solar cell BEAM robot crowd.

We managed to power a small motor off it. :D

Offline jsmokerTopic starter

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Re: Low Voltage DC - DC multiplier
« Reply #8 on: February 18, 2011, 01:35:37 PM »
@Soeren: I thought about connecting them in series, but cells are ~$20 w/o shipping and I'd have to figure a way to heat them both up on one side at the same time so decided against it.  A secondary source had crossed my mind, but I want to keep it self powered.  The germanium transistor does sound interesting though.  I'll look into it:)

@admin (aka pikachu): Long time no see. how've you been?

Offline Admin

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Re: Low Voltage DC - DC multiplier
« Reply #9 on: February 18, 2011, 03:37:24 PM »
@admin (aka pikachu): Long time no see. how've you been?
Pretty good . . . I see you are still in the DC area (I'm near Silver Spring) . . . you working or still a student?

Offline madsci1016

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Re: Low Voltage DC - DC multiplier
« Reply #10 on: February 18, 2011, 04:00:33 PM »
@admin (aka pikachu)

Explain.

NVM, Admin did.
« Last Edit: February 18, 2011, 04:10:47 PM by madsci1016 »

Offline madsci1016

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Re: Low Voltage DC - DC multiplier
« Reply #11 on: February 18, 2011, 04:04:43 PM »
It's a Seebeck effect thermoelectric junction (a glorified thermocouple).  I want to show it's effect with a LED for demonstration purposes. 

BTW, I've done this demo for kids, but with a 1.5V motor spinning a painted paper disk. Boiling water and dry ice on either side.

Offline jsmokerTopic starter

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Re: Low Voltage DC - DC multiplier
« Reply #12 on: February 21, 2011, 09:07:08 AM »
Quote
BTW, I've done this demo for kids, but with a 1.5V motor spinning a painted paper disk. Boiling water and dry ice on either side.

Was the Boiling and Ice water enough potential to power the 1.5V motor?  Did you actually get 1.5V, or was it spinning but under powered?

Offline jsmokerTopic starter

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Re: Low Voltage DC - DC multiplier
« Reply #13 on: February 21, 2011, 09:08:43 AM »
Quote
you working or still a student?


Still a student, trying to finish up.  Cool dissertation topic though...active acoustic cloak.

Offline madsci1016

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Re: Low Voltage DC - DC multiplier
« Reply #14 on: February 21, 2011, 10:43:24 AM »
Quote
BTW, I've done this demo for kids, but with a 1.5V motor spinning a painted paper disk. Boiling water and dry ice on either side.

Was the Boiling and Ice water enough potential to power the 1.5V motor?  Did you actually get 1.5V, or was it spinning but under powered?

Dry Ice
, not ice water. And never measured, but definitely underpowered. That's why it just spins a painted disk so the kids could see it doing something.

Offline madsci1016

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Re: Low Voltage DC - DC multiplier
« Reply #15 on: February 21, 2011, 10:46:26 AM »
.active acoustic cloak.

You aren't the one working on the underwater acoustic cloak are you? That's causing us all sorts of headaches on my Navy Base.

Offline Admin

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Re: Low Voltage DC - DC multiplier
« Reply #16 on: February 21, 2011, 11:39:52 AM »
Quote
you working or still a student?


Still a student, trying to finish up.  Cool dissertation topic though...active acoustic cloak.

Can I come by your lab and see (hear?) it? :P

Still at UMD?

 


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